On Feb. 13, three men were arrested on the road to Mazatlán, including a man called “19,” believed to be the new head assassin for one of Mr. Guzmán’s senior officers, Ismael (Mayo) Zambada. On Feb. 17, another senior leader was captured with 4,000 hollowed-out cucumbers and bananas filled with cocaine.

A half-dozen others followed and with each arrest and seizure, Mexican officials made sure to emphasize that they were seeking Mr. Zambada. The true nature of the operation never leaked — in part because of Mr. Guzmán’s legend. No one seemed to suspect that he would come down from his secret hiding spots in the mountains of Sinaloa, or further afield, in Guatemala or wherever else.